A Different Kind of Cushing’s
Most articles about canine Cushing’s describe the naturally occurring disease — a tumor in the pituitary gland or an adrenal gland driving cortisol too high. But there is a second, very different form that is entirely man-made: iatrogenic Cushing’s, caused not by a tumor but by steroid medication given to the dog. “Iatrogenic” simply means “caused by treatment.”
It matters because the cause, the diagnosis, and — encouragingly — the outlook are all different from the spontaneous disease.
What Causes It
Corticosteroids such as prednisone, prednisolone, and dexamethasone are powerful, useful drugs for allergies, itching, immune conditions, and inflammation. But given at high doses or for long stretches, the body reacts to that extra steroid exactly as if the adrenal glands were overproducing it — because, to the tissues, cortisol and prescribed steroid look the same. The result is a Cushing’s picture created from outside the body.
It is not only pills and injections. Iatrogenic Cushing’s has been documented from steroid-containing eye drops, ear medications, and even topical skin creams — including cases traced to a dog absorbing a steroid cream meant for its owner. Any route that delivers enough steroid for long enough can do it.
The Signs
Because the driver is the same excess steroid effect, the signs mirror naturally occurring Cushing’s: increased thirst and urination, a larger appetite, a pot-bellied appearance, thinning skin and hair loss, muscle weakness, and a rise in urinary and skin infections. If your dog is on long-term steroids and starts to look and act this way, iatrogenic Cushing’s should be on the list.
How It Is Diagnosed
This is where iatrogenic Cushing’s reveals itself. On an ACTH stimulation test — the test of choice here — a dog with iatrogenic disease shows a blunted, suppressed response: the adrenal glands, chronically told to stand down by all that outside steroid, produce very little cortisol when challenged. That low-response pattern is essentially the opposite of what is often seen in the naturally occurring disease, and combined with the medication history it makes the diagnosis clear.
Treatment: Taper, Never Stop Abruptly
The logical fix — stop the steroid — is right in principle but dangerous if done suddenly. After long-term steroid use, the dog’s own adrenal glands may have gone dormant and cannot immediately resume normal cortisol production. Pulling the drug overnight can trigger a life-threatening adrenal insufficiency (an Addisonian-type crisis). For that reason, steroids must be withdrawn slowly, on a tapering schedule set by your veterinarian, giving the adrenal glands time to wake back up. Any underlying condition the steroid was treating also has to be managed another way.
The Good News: It Is Often Reversible
Unlike tumor-driven Cushing’s, iatrogenic Cushing’s usually resolves once the steroid is safely tapered off and the adrenal glands recover. With early recognition and a careful taper, the prognosis is generally good, and the Cushing’s signs fade. The key preventive lesson is to use the lowest effective steroid dose for the shortest necessary time, and to monitor dogs who need steroids long-term — something to discuss openly with your vet rather than stopping medication on your own.
The Bottom Line
Iatrogenic Cushing’s is Cushing’s syndrome created by steroid medication rather than a tumor. It looks like the real thing, it is confirmed with an ACTH stimulation test showing a suppressed response, and it is treated by slowly and safely tapering the steroid — never stopping cold. Caught early, it is one of the few forms of Cushing’s that typically reverses.
Sources
- Merck Veterinary Manual — Cushing Disease (Pituitary-Dependent Hyperadrenocorticism) in Animals. merckvetmanual.com
- VCA Animal Hospitals — Steroid Treatment: Long-Term Effects in Dogs. vcahospitals.com
- “Iatrogenic Cushing’s syndrome in a dog from owner’s topical corticosteroid.” PubMed. pubmed.ncbi.nlm.nih.gov
